Hallo Idefix,
Have you checked the small lock system behind the driver's seat ?
It moved from left to right and caused noise on mine when I was driving top down.
I put a little piece of felt here, and the rattle never came back for me.   
 
Test it and drive top down.
 
		 
				
	
 
  ) schaut, dann findet man sehr viele Beiträge in anderen Autoforen hierzu.
 ) schaut, dann findet man sehr viele Beiträge in anderen Autoforen hierzu. .
 . .
 . !
 !